Luarocks with rockspec to "master" HEAD

Hi all

Following Clement's great rockspec writing, I've merged luarocks and master and added a rockspec dubbed torch-7.99 that will point to the HEAD of master, so that we can always easily install the cutting-edge version and not be slowed down by waiting for a specific tag to be added.

I've discussed with @koraykv who suggested to send this pull request.

<b>Note:</b> for now the rocklet refers to my fork (since it's not merged in your repo yet), so after pulling you will want to change line 5 from
```lua
  url = "git://github.com/jucor/torch.git",
```
to
```lua
  url = "git://github.com/andresy/torch.git",
```

Julien